scholarly journals Reliability-Based Ultimate Limit State Design of Micropiles in Ontario Soils

2021 ◽  
Author(s):  
Alexandre P. R. P. Almeida
Keyword(s):  
Bond Strength ◽  
Failure Load ◽  
Limit State ◽  
Accurate Estimation ◽  
Ultimate Limit State ◽  
Resistance Factors ◽  
Ground Conditions ◽  
Load Tests ◽  
Ultimate Limit State Design ◽  
Ultimate Limit

The design practice of micropiles in Ontario soils under the ultimate limit state was improved through both statistical and reliability analyses of a database of 40 micropile load tests. Micropile design is extremely dependent on engineering experience and judgement due to the lack of an accurate estimation of the bond strength. The FHWA manual of micropiles only provides wide ranges of bond strength in different ground conditions. Micropile load tests were conducted by Keller Foundations Ltd and collected for this study. From a statistical analysis, Fuller and Hoy’s method was selected as the best method to estimate the failure load from non-failed tests. Adjusted parameters were given to predict the bond strength of micropiles. A method was proposed to estimate the contributions from the cased length and the tip to the total resistance. In the end, a reliability analysis was conducted and the resistance factors were recalibrated.

scholarly journals Reliability-Based Ultimate Limit State Design of Micropiles in Ontario Soils

2021 ◽  
Author(s):  
Alexandre P. R. P. Almeida
Keyword(s):  
Bond Strength ◽  
Failure Load ◽  
Limit State ◽  
Accurate Estimation ◽  
Ultimate Limit State ◽  
Resistance Factors ◽  
Ground Conditions ◽  
Load Tests ◽  
Ultimate Limit State Design ◽  
Ultimate Limit

The design practice of micropiles in Ontario soils under the ultimate limit state was improved through both statistical and reliability analyses of a database of 40 micropile load tests. Micropile design is extremely dependent on engineering experience and judgement due to the lack of an accurate estimation of the bond strength. The FHWA manual of micropiles only provides wide ranges of bond strength in different ground conditions. Micropile load tests were conducted by Keller Foundations Ltd and collected for this study. From a statistical analysis, Fuller and Hoy’s method was selected as the best method to estimate the failure load from non-failed tests. Adjusted parameters were given to predict the bond strength of micropiles. A method was proposed to estimate the contributions from the cased length and the tip to the total resistance. In the end, a reliability analysis was conducted and the resistance factors were recalibrated.

Geotechnical resistance factors for ultimate limit state design of deep foundations in cohesive soils

2011 ◽  
Vol 48 (11) ◽  
pp. 1729-1741 ◽  
Author(s):  
Mehrangiz Naghibi ◽  
Gordon A. Fenton
Keyword(s):  
Limit State ◽  
Cohesive Soil ◽  
Ultimate Limit State ◽  
Deep Foundations ◽  
Cohesive Soils ◽  
Deep Foundation ◽  
Resistance Factors ◽  
Limit State Design ◽  
Ultimate Limit State Design ◽  
Ultimate Limit

This paper investigates the ultimate limit state load and resistance factor design (LRFD) of deep foundations founded within purely cohesive soils. The geotechnical resistance factors required to produce deep foundation designs having a maximum acceptable failure probability are estimated as a function of site understanding and failure consequence. The probability theory developed in this paper, used to determine the resistance factors, is verified by a two-dimensional random field Monte Carlo simulation of a spatially variable cohesive soil. The agreement between theory and simulation is found to be very good, and the theory is then used to derive the required geotechnical resistance factors. The results presented in this paper can be used to complement current ultimate limit state design code calibration efforts for deep foundations in cohesive soils.

Geotechnical resistance factors for ultimate limit state design of deep foundations in frictional soils

2011 ◽  
Vol 48 (11) ◽  
pp. 1742-1756 ◽  
Author(s):  
Gordon A. Fenton ◽  
Mehrangiz Naghibi
Keyword(s):  
Limit State ◽  
Friction Angle ◽  
Soil Mass ◽  
Ultimate Limit State ◽  
Deep Foundations ◽  
Resistance Factors ◽  
Limit State Design ◽  
Ultimate Limit State Design ◽  
Ultimate Limit ◽  
Frictional Soils

This paper investigates the probabilistic nature of ultimate limit state failures of deep foundations in purely frictional soils (e.g., sands). In so doing, the theory required to predict both the probability of ultimate limit state failure and the resistance factors needed to avoid this limit state are proposed. The proposed resistance factors are functions of site understanding and failure consequence, and the theory leading to these resistance factors is validated via Monte Carlo simulation of a two-dimensional spatially variable random field. In both the theory and the simulation, a pile is assumed to be placed vertically at a certain position in the soil mass, and the soil is sampled at various distances from the pile to come up with characteristic soil properties (namely friction angle) for use in the pile design. Agreement between theory and simulation is found to be very good. The theoretical model is then employed to determine upper bound geotechnical resistance factors, which can be used to complement current ultimate limit state design code calibration efforts. An example of such a calibration is presented.

Practical Reliability-Based Design Approach for Foundation Engineering

1996 ◽  
Vol 1546 (1) ◽  
pp. 94-99 ◽  
Author(s):  
Kok Kwang Phoon ◽  
Fred H. Kulhawy
Keyword(s):  
Research Study ◽  
Limit State ◽  
Drilled Shafts ◽  
Ultimate Limit State ◽  
Foundation Engineering ◽  
Reliability Level ◽  
Reliability Based Design ◽  
Ultimate Limit State Design ◽  
Ultimate Limit ◽  
Selection Of

A research study was completed recently that was directed toward the development of practical, reliability-based design (RBD) equations specifically for foundation engineering. Some of the key RBD principles used in the study are presented. The important considerations involved in the development of practical and robust RBD criteria are emphasized. In particular, the selection of an appropriate reliability assessment technique and the careful characterization and compilation of geotechnical variabilities are important because of their central role in the calculation of the probability of failure and the assessment of the target reliability level. An overview of a simplified RBD approach is given, and an application of this approach to the ultimate limit state design of drilled shafts under undrained uplift loading is discussed.

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